1. Field of the Invention
The present invention is generally related to the field of bookbinding and, in particular, to the binding a stack of sheets into a hardcover book.
2. Description of Related Art
There are several well-known techniques for binding books. One technique, commonly referred to as perfect binding, is used to bind a stack of sheets using a hot melt adhesive. The adhesive is also used to secure a soft cover to the bound stack. Referring to the drawings, the perfect binding process is illustrated in schematic form in FIGS. 1A-1C. This process is typically automated. The stack 30 to be bound is secured in a clamping mechanism illustrated by clamp members 32A and 32B. A grinding mechanism 31 at a first station is used to grind the edge 30A of the stack. This is typically accomplished using high speed rotating cutting blades 31A. The roughened edge of the stack will facilitate the absorption of hot melt adhesive and ensures that each sheet will contact the adhesive.
Next, as illustrated in FIG. 1B, the stack is moved to a further station where hot melt adhesive 34 is applied to the edge of the stack. While the adhesive is still molten, the stack is moved to a third station as shown in FIG. 1C where a folded paper cover 36 is automatically folded around and secured to the stack by way of molten adhesive 34. If needed the stack 30 and/or cover 36 are then trimmed after the adhesive has had an opportunity to cool.
In some applications, a pair of special end leafs are added to the stack 30 prior to binding for the purpose of enhancing the appearance of the bound book. FIG. 2 shows one end leaf 38 that includes a folded sheet of relatively heavy paper that forms sheets 40A and 40B, joined at fold 40C. An elongated, relatively stiff, spacer member 46 is attached to the lower portion of sheet 40A and extends slightly below the fold line 40C, typically ⅛ of an inch. End leaf 38 is positioned adjacent one outer sheet of a stack 30 and a second similar end leaf 42 is positioned adjacent the other outer sheet of stack 30. The dimensions of end leafs 38 and 42, including the respective spacer members 46 and 48, correspond to the dimensions of the sheets to be bound. When the stack and end leafs are subjected to the grinding step previously mentioned in connection with FIG. 1A, a small portion of the end of the stack and much of the spacer members 46 and 47 are ground away. The spacer members 46 and 48 operate as sacrificial elements to prevent sheets 40A, 40B, 44A and 44B and the folds connecting the sheets from being damaged in the grinding step.
Once the cover 36 has been applied to the bound stack, outer sheets 40A and 44A are glued to the respective inner surfaces of the cover. Thus, when the cover is opened at one end, the reader can see, for example, sheets 40B and 40A connected near the spine at fold 40C. When the cover is opened at the other end, sheets 40A, 40B and fold 44C can be seen. Thus, the prefect bound book has the appearance that approaches that of a traditional bound book. Note also that the position of each of end leafs 38 and 42 could be reversed so that spacer members 46 and 48 are positioned on the outside of the assembly rather than being positioned adjacent the respective outer sheets of stack 30. In any event, in this application, the only functioned performed by end leafs 38 and 42 is cosmetic.
The above-described prior art perfect binding method is very popular, particularly for fairly high volume production. It is possible to produce a hardcover book starting with the bound stack or book block 30 produced at the end of the step described in connection with FIG. 1B. A hardcover is applied to the book block 30 using what can be termed a cold glue, as contrasted with the hot melt adhesive used in the perfect binder machine. Unfortunately, there is an interface between the hot melt adhesive and the cold glue that has a tendency to fail over time.
The present invention permits a hardcover book to be produced using conventional perfect binding equipment and related technology. The resultant hardcover book structure avoids the above-mentioned problem resulting from the interface between the hot melt adhesive and cold glue. These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following Detailed Description of the Invention together with the drawings.